1. Field of the Invention
The present invention relates to lenticular arrays and methods and devices for absorbing undesired light falling on such arrays.
2. Description of the Prior Art
In apparatus using front projection screens, an image source in front of the screen projections an image onto a screen. The screen reflects light from the image back to viewers in an audience field, also located in front of the screen.
A problem encountered in these front projection systems is that the image contrast is reduced by the presence of ambient light. This is particularly troublesome in those applications in which a dedicated projection room is not practical, for example, projection television for the consumer market. In such cases, the source and character of undesired light such as ambient light is generally unpredictable and uncontrollable.
Image contrast of front projection screens has been increased by various types of blackening to absorb ambient light without interfering with the desired projected light constituting the image. Black masking in the form of light absorbing filaments located in the grooves between the light-spreading lenticules is illustrated in FIG. 2 of the parent case, while in FIG. 3 black masking is accomplished by filling a portion of the grooves between the light spreading lenticules with discrete black particles and by containing the particles by means of a skin which extends between the lenticules over the groove. This black mask construction is also described in U.S. Pat. No. 4,605,283, assigned to the same assignee.
All of the above types of blackening create manufacturing and operating difficulties. The black filaments tend to break and are difficult to position. Particles are difficult to maintain in the groove before being fixed and have a tendency to spread over the tips of the lenticular elements, thereby interfering with the image-forming light. Furthermore, the placement of either filaments or particles within the grooves results in some portion of blackening material touching the sidewalls or being sufficiently close, i.e. within about a micron, that the overall efficiency of the screen is reduced because a portion of the desired light instead of being reflected is absorbed.